An emerging trend in biotechnology and medical diagnostics is to improve the speed and sensitivity of molecular analyses via label-free, noninvasive techniques that exploit electrochemical and microelectronic technologies. Label-free detection methods have been widely utilized to monitor analyte concentrations in vitro, most commonly using either ion-sensitive semiconductor field effect transistors or conductive polymeric devices. These label-free technologies are scalable, with the added advantage that they can be used to quantitatively measure a variety of molecular concentration gradients in a highly parallel fashion via surface modifications of individual electrodes. Furthermore, label-free detection technologies are advantageous over traditional optical and radiolabel techniques, since they can be used to monitor cells and tissues over long periods of time without the onset of cytotoxic side effects. Although the biocompatibility and high-throughput of label-free technologies are favorable, a critical downfall of existing devices is that they do not permit an investigator to actively mediate molecular binding at the sensor surface. Consequently, most label-free devices cannot be used to control adsorption of biomolecules to a functionalized surface in an on-off fashion, nor can these devices be used to dynamically detect molecular gradients within cell or tissue microenvironments.